Cobalt Filling of Interconnects

ABSTRACT

Compositions and methods of using such compositions for electroplating cobalt onto semiconductor base structures comprising submicron-sized electrical interconnect features are provided herein. The interconnect features are metallized by contacting the semiconductor base structure with an electrolytic composition comprising a source of cobalt ions, a suppressor, a buffer, and one or more of a depolarizing compound and a uniformity enhancer. Electrical current is supplied to the electrolytic composition to deposit cobalt onto the base structure and fill the submicron-sized features with cobalt. The method presented herein is useful for superfilling interconnect features.

FIELD OF THE INVENTION

The compositions and processes described herein generally relate toelectrolytic deposition chemistry and methods for depositing cobalt andcobalt alloys. These compositions and methods are used for cobalt-basedmetallization of interconnect features in semiconductor substrates.

BACKGROUND OF THE INVENTION

In damascene processing, electrical interconnects are formed in anintegrated circuit substrate by metal-filling of interconnect featuressuch as vias and trenches, formed in the substrate. Copper is apreferred conductor for electronic circuits. Unfortunately, when copperis deposited on silicon substrates it can diffuse rapidly into both thesubstrate and dielectric films (such as SiO₂ or low k dielectrics).Copper also has a tendency to migrate from one location to another whenelectrical current passes through interconnect features in service,creating voids and hillocks. Copper can also diffuse into a device layerthat is built on top of a substrate in a multilayer device application.Such diffusion can be detrimental to the device because it can damage anadjacent interconnect line and/or cause electrical leakage between twointerconnects. Electrical leakage can result in an electrical short andthe corresponding diffusion out of the interconnect feature can disruptelectrical flow.

In recent years, along with the reduction in size and desired increasein the performance of electronic devices, the demand for defect free andlow resistivity interconnects in the electronic packaging industry hasbecome critical. As the density of an integrated circuit within amicroelectronic device continues to increase with each generation ornode, interconnects become smaller and their aspect ratios generallyincrease. The build-up process, using barrier and seed layers, prior todamascene copper electroplating, now suffers from disadvantages that arebecoming more evident as the demand for higher aspect ratio features andhigher quality electronic devices increases. As a result, there is aneed for more suitable plating chemistry to enable defect freemetallization.

When submicron vias and trenches are filled by electrolytic depositionof copper, it is generally necessary to first deposit a barrier layer onthe walls of the cavity to prevent the diffusion and electromigration ofcopper into the surrounding silicon or dielectric structure. In order toestablish a cathode for the electrodeposition, a seed layer is depositedover the barrier layer. Barrier and seed layers can be very thin,especially where the electroplating solution contains a properformulation of accelerators, suppressors, and levelers. However, as thedensity of electronic circuitry continues to increase, and the entrydimensions of vias and trenches become ever smaller, even very thinbarrier and seed layers progressively occupy higher fractions of theentry dimensions. As the apertures reach dimensions below 50 nm,especially less than 40 nm, 30 nm, 20 nm, or even less than 10 nm (8 or9 nm), it becomes increasingly difficult to fill the cavity with acopper deposit that is entirely free of voids and seams. The mostadvanced features have bottom widths of only 2-3 nm, a middle width ofabout 4 nm, and a depth of 100 to 200 nm, translating to an aspect ratioof between about 25:1 and about 50:1.

Electrolytic deposition of cobalt is performed in a variety ofapplications in the manufacture of microelectronic devices. For example,cobalt is used in capping of damascene copper metallization employed toform electrical interconnects in integrated circuit substrates. However,because cobalt deposits have higher resistivity, such processes have notpreviously offered a satisfactory alternative to electrodeposition ofcopper in filling vias or trenches to provide the primary interconnectstructures.

SUMMARY OF THE INVENTION

Described herein are compositions that are useful for the electrolyticdeposition of cobalt. The electrolytic compositions comprise: a sourceof cobalt ions; a suppressor compound; a buffering agent; optionally auniformity enhancer; and optionally a depolarizing compound. Thecompositions described herein are useful for electrodeposition ofcobalt, wherein the composition is essentially free of divalent sulfurcompounds.

Such compositions are used in a process for filling a submicron cavityin a dielectric material wherein the cavity has a wall region comprisinga contact material, the process comprising contacting a dielectricmaterial comprising the cavity with an electrolytic cobalt platingcomposition under conditions effective to deposit cobalt on the wallregions, wherein the cobalt plating composition comprises a source ofcobalt ions, a suppressor compound, a uniformity enhancer, a bufferingagent, and one or more of a depolarizing compound and a uniformityenhancer. The composition may further include a compound that functionsas a stress reducer.

The composition of the current invention can be summarized as acomposition for the electrolytic deposition of cobalt comprising:

-   -   a source of cobalt ions;    -   a suppressor compound;    -   a buffering agent; and    -   one or more of a depolarizing compound and a uniformity        enhancer;

wherein the composition is at least substantially free of divalentsulfur compounds.

Further described are methods for filling submicron features of asemiconductor integrated circuit device by electrodeposition using thecompositions described herein.

The method of the current invention can be summarized as a method forelectroplating a cobalt deposit onto a semiconductor base structure,wherein the semiconductor base structure comprises a metallizingsubstrate comprising submicron-sized electrical interconnect features,the method comprising the steps of:

-   -   a) contacting the metallizing substrate with an electrolytic        composition comprising:        -   a source of cobalt ions;        -   a suppressor compound;        -   a buffering agent; and        -   one or more of a depolarizing compound and a uniformity            enhancer; and    -   wherein the composition is at least substantially free of        divalent sulfur compounds; and    -   b) supplying electrical current to the electrolytic composition        to deposit cobalt onto the base structure and fill the        submicron-sized electrical interconnect features with cobalt.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic illustration of a cobalt filled featureprepared by the method of the current invention.

FIG. 2 shows a schematic illustration demonstrating how an angle cutcross-section is taken using a conventional focus ion beam/scanningelectron microscope technique. This technique is used to analyze theplating in the interconnect features.

FIG. 3 shows polarization curves comparing ethoxylated propargyl alcoholand sodium propargyl sulfonate in cobalt VMS with ethoxylated propargylalcohol and ethoxylated, propoxylated, ethylene diamine in cobalt VMS.The polarization curves show 20 mg/L ethoxylated propargyl alcohol+150mg/L sodium propargyl sulfonate and 20 mg/L ethoxyglated propargylalcohol+1000 mg/L ethoxylated, propoxylated ethylene diamine in the VMS(virgin makeup solution) comprising 2.95 g/L Co (Co ion concentration)and 30 g/L boric acid for 10 seconds with no current at the workingelectrode followed by 2 mA/cm² at 100 rpm and pH 3, wherein the workingbath is degassed (dissolved oxygen <2 ppm).

FIG. 4 shows polarization curves for separate injections of ethoxylatedpropargyl alcohol followed by sodium propargyl sulfonate into cobaltVMS. The VMS comprises 2.95 g/L Co (Co ion concentration) and 30 g/Lboric acid, has a pH of 3, a current density of 4 mA/cm², rotation rateof 1000 rpm, is degassed (dissolved oxygen <2 ppm), and operates at roomtemperature.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Cobalt-based electrolytic plating compositions and methods have beendeveloped for use in electrolytic deposition of cobalt as an alternativeto copper in the manufacture of semiconductor integrated circuitdevices. More particularly, the compositions and methods of theinvention are effective for filling submicron features of such devices.

The cobalt-based plating compositions described herein contain a sourceof cobalt ions. Although various cobaltous salts can be used, CoSO₄ ishighly preferred. One source of cobaltous ions is cobalt sulfateheptahydrate. The composition is formulated with a cobalt salt in aconcentration which is sufficient to provide between about 1 and about50 g/L of Co⁺² ions, preferably between about 2 and about 10 g/L, andmore preferably between about 2 and about 5 g/L.

The composition comprises one or more suppressor compounds whichpreferably comprises acetylenic alcohol compounds or derivativesthereof. One preferred suppressor is ethoxylated propargyl alcohol.Other preferred suppressor compounds include, but are not limited to,propargyl alcohols, ethoxylated propargyl alcohols, propoxylatedpropargyl alcohols, ethoxylated, propoxylated propargyl alcohols, areaction product of ethoxylated propargyl alcohol and 1,4-butanedioldiglycidyl ether, diethylene glycol bis(2-propynyl) ether,1,4-bis(2-hydroxyethoxy)-2-butyne, 2-butyne-1,4-diol, 4-pentyne-1-ol,2-methyl-3-butyne-2-ol, 3-methyl-1-pentyne-3-ol, 3-butyne-2-ol, andcombinations of one or more of the foregoing. The concentration of thesuppressor is preferably between about 1 and about 250 mg/L, and morepreferably between about 10 and about 70 mg/L, and most preferablybetween about 20 and about 50 mg/L.

The composition may comprise one or more uniformity enhancing compoundswhich preferably comprise aminic polyol compounds or derivativesthereof. A preferred uniformity enhancer is ethoxylated, propoxylatedtriisopropanolamine. In one embodiment, the uniformity enhancer has amolecular weight of about 5000 g/mol. Other preferred uniformityenhancing compounds include ethoxylated, propoxylated ethylene diamine,ethoxylated, propoxylated diethylene triamine and ethoxylated,propoxylated triethylenetetramine. The concentration of the uniformityenhancer is preferably between about 10 and about 4000 mg/L, and morepreferably between about 100 and about 2000 mg/L, and most preferablybetween about 250 and about 1000 mg/L.

The composition may comprise one or more depolarizing compounds. In oneembodiment the one or more depolarizing compounds comprises terminalunsaturated compounds or derivatives thereof. These compounds arecapable of depolarizing the plating potential. In one embodiment, thedepolarizing compound may be selected from the group consisting ofsodium propargyl sulfonate, acetylenedicarboxylic acid, acrylic acid,propiolic acid, vinyl phosphonate, and mixtures thereof. One preferreddepolarizing compound is sodium propargyl sulfonate. The concentrationof the depolarizing compound is preferably between about 0.1 and about5000 mg/L, and more preferably between about 10 and about 1000 mg/L, andmost preferably between about 100 and about 500 mg/L.

The electrolytic cobalt composition, also optionally, but preferablycomprises a buffer to stabilize the pH. One preferred buffer is boricacid (H₃BO₃), which may be incorporated into the composition in aconcentration between about 5 and about 50 g/L, preferably between about15 and about 40 g/L. The pH of the composition is preferably maintainedin the range of about 0.5 to about 8, preferably from about 2 to about5.

The electrolytic composition described herein is also preferablysubstantially free of copper ions. Although very minor coppercontamination may be difficult to avoid, it is particularly preferredthat the copper ion content of the bath is no more than 20 ppb, e.g., inthe range of 0.1 ppb to 20 ppb. This composition, as defined herein, issubstantially free of copper ions when there are less than 20 ppb copperions in solution.

The electrolytic composition is preferably free of any functionalconcentration of reducing agents that are effective to reduce cobaltousions (Co²⁺) to metallic cobalt (Co⁰). A functional concentration isdefined herein as any concentration of an agent that either is effectiveto reduce cobaltous ions in the absence of electrolytic current or isactivated by an electrolytic current or electrolytic field to react withcobaltous ions.

In one embodiment, the electrolytic composition comprises between about1 and about 50 g/L cobalt ions; between about 1 and about 100 mg/L of asuppressor compound; optionally between about 10 mg/L and about 4000mg/L of a uniformity enhancer; between about 5 mg/L and about 50 g/Lbuffer, and optionally a depolarizing compound between about 0.1 mg/Land about 1000 mg/L. The pH of the composition is preferably betweenabout 1.5 and about 7.5, more preferably between about 2 and about 5.

In one embodiment, the electrolytic composition comprises between about5 and about 10 g/L cobalt ions, between about 15 and about 65 mg/L of asuppressor selected from the group consisting of propargyl alcohol andethoxylated propargyl alcohol, optionally between about 100 and about1000 mg/L of the uniformity enhancer, between about 15 and about 40 g/Lbuffer, optionally a depolarizing compound between about 10 mg/L and 500mg/L and the balance substantially water. The pH is preferably adjustedto a value between about 2.5 and about 3.5. Sulfuric acid is preferredfor pH adjustment.

The electrolytic composition described herein can be used in a methodfor filling submicron features of a semiconductor base structure. Thesubmicron features comprise cavities in the base structure that aresuperfilled by rapid bottom-up deposition of cobalt. A metallizingsubstrate comprising a seminal conductive layer is formed on theinternal surfaces of the submicron features, e.g., by physical vapordeposition of metal seed layer, preferably a cobalt metal seed layer, ordeposition of a thin conductive polymer layer. A submicron electricalinterconnect feature has a bottom, sidewalls, and top opening. Themetallizing substrate is applied to the bottom and sidewall, andtypically to the field surrounding the feature. The metallizingsubstrate within the feature is contacted with the electrolyticcomposition and current is supplied to the electrolytic composition tocause electrodeposition of cobalt that fills the submicron features. Byco-action of the suppressor, optional uniformity enhancer, and optionaldepolarizing compound, a vertical polarization gradient is formed in thefeature in which filling will occur by bottom up deposition at a rate ofgrowth in the vertical direction which is greater than a rate of growthin the horizontal direction, yielding a cobalt interconnect that issubstantially free of voids and other defects.

To implement the electrodeposition method, an electrolytic circuit isformed comprising the metallizing substrate, an anode, the aqueouselectrolytic composition, and a power source having a positive terminalin electrically conductive communication with the anode and a negativeterminal in electrically conductive communication with the metallizingsubstrate. Preferably, the metallizing substrate is immersed in theelectrolytic composition. An electrolytic current is delivered from thepower source to the electrolytic composition in the circuit, therebydepositing cobalt on the metallizing substrate.

The electrodeposition process is preferably conducted at a bathtemperature in the range of about 5° C. to about 80° C., more preferablybetween about 20° C. and about 50° C., and a current density in therange between about 0.01 and about 20 mA/cm², preferably between about0.3 and about 10 mA/cm². Optionally, the current may be pulsed, whichcan provide improvement in the uniformity of the deposit. On/off pulsesand reverse pulses can be used. Pulse plating may enable relatively highcurrent densities, e.g., >8 mA/cm² during cobalt deposition.

Cold and hot entry methods can be used with this plating composition.Cold entry refers to starting the current after the electrodeestablishes contact with plating bath. Hot entry refers to starting thecurrent at the moment when the electrode establishes contact withplating bath. In one embodiment, it was found that cold entry provides afavorable result.

In addition to using direct current, multi-plating step current andramping current waveform can be used in the instant invention.Multi-plating step current waveform means that after open circuit time(no current), if cold entry is used, i₁ is applied for certain time,then i₂ is applied for certain time, then i_(n) (n>1) is applied.Typically, i₁ is the smallest current density, and then current densitygradually increases. Ramping current waveform means that after opencircuit time, if cold entry is used, current density starts at i₁, andgradually increases to i₂ at changing rate, given in mA/cm² s. Apreferred current waveform is open circuit time for 10 seconds, 0.5mA/cm² for 4 minutes and 2 mA/cm² for 2 minutes to fully fill thefeature with 7 nm opening and 180 nm depth. If overplate of the via ortrench is needed, another plating step at 10 mA/cm² for 60 seconds canbe used to achieve 150 nm of overplate.

When divalent sulfur compounds are excluded from the plating bath, thesulfur content of the cobalt deposit is lowered, with consequentbeneficial effects in chemical mechanical polishing and circuitperformance.

The electrolytic composition is substantially free of divalent sulfurcompounds if the concentration of divalent sulfur in the platingsolution is not greater than 1 mg/l. Preferably, the concentration ofcompounds containing divalent sulfur atoms is not greater than 0.1 mg/l.Still more preferably, the concentration of divalent sulfur atoms isbelow the detection level using analytical techniques common to thoseskilled in the art of metal plating.

To reduce internal stress in the cobalt deposit, the electrolyticcomposition can include a stress reducer such as saccharin. When used,saccharin is present in the electrolytic composition in a concentrationbetween about 10 and about 300 ppm, more preferably between about 100and about 200 ppm.

It has been surprisingly discovered not only that submicron features canbe effectively superfilled using compositions that are devoid ofaccelerators and other compounds that comprise divalent sulfur, but thatcobalt can be effectively deposited from a plating bath that comprisesno accelerator at all. When the plating bath contains a suppressor suchas those described above, and a uniformity enhancer is described herein,the superfilling process proceeds satisfactorily without the need for anaccelerator. The suppressors in the current invention help drive currentinto the features to make bottom-up filling efficient and the uniformityenhancing additives help improve deposit uniformity. The composition issubstantially free of reducing agents that reduce Co²⁺ to Co⁰, divalentsulfur, copper ions, nickel ions and iron ions.

It has also been found that certain depolarizing compounds can functionin conjunction with the suppressor compounds as described herein. Thesecompounds depolarize the plating potential to efficiently plateinterconnect features. FIGS. 3 and 4 demonstrate the capabilities of thedepolarizing compounds in combination with the suppressor compoundsdescribed herein. FIG. 3 shows that ethoxylated propargyl alcohol andethoxylated, propoxylated ethylene diamine have stable platingpotential, but the combination of ethoxylated propargyl alcohol andsodium propargyl sulfonate have clear depolarization. The depolarizationcan benefit gap fill performance, with proper plating conditions, bydriving more current into the trench. FIG. 4 shows the effects ofseparate injections of ethoxylated propargyl alcohol and sodiumpropargyl sulfonate in cobalt VMS, wherein the injection of ethoxylatedpropargyl alcohol at about 600 seconds causes polarization in potentialfor about 270 mV and the injection of sodium propargyl sulfonate atabout 1500 seconds causes depolarization in potential for about 120 mV.Acetylenedicarboxylic acid, acrylic acid, vinyl phosphonate, andpropiolic acid have been identified as having similar depolarizationproperties to sodium propargyl sulfonate.

Bottom-up fill means that deposit grows up from the bottom of features,like a trench. Bottom-up fill can be classified as V or U shaped. AV-shape bottom-up has a pointier bottom, and a U-shape bottom-up hasmore leveled bottom. U-shape bottom-up filling is preferred, as V-shapebottom-up filling can generate seams. Conformal fill means that adeposit grows from sidewalls and bottom to the center of features. Themost challenging features usually have very large aspect ratios (aspectratio is the ratio of depth over width), and conformal fill typicallymakes a seam at the center of such features. A seam can be vague orclear depending on fill mechanism. However, after annealing, any seamcan make seam voids or center voids.

Uniformity of the cobalt deposit is an important requirement. Howeverthere is often a trade-off between gap fill and uniformity. The higherthe suppressor concentration in a plating composition, the better thefill performance can be, but uniformity can often become worse. As aresult, additives have been introduced into the composition to improveuniformity without any negative impact on fill performance, so that theoperating window of the suppressor can be expanded. The results of usingthese uniformity enhancing additives and optional accelerating compoundsin combination with the described suppressors provided unexpectedlyefficient methods to superfill submicron-sized interconnect featureswith cobalt. Another benefit of using the uniformity enhancing additivesis that it allows for wider operating ranges with respect to thesuppressor concentration, the current density, rotation rate and othertypically limited factors.

The novel compositions and methods are effective in the preparation ofsemiconductor integrated circuit devices comprising the semiconductorbase structure and submicron interconnect features filled with cobalt.Providing cobalt interconnects is especially advantageous where theinterconnect features have a width or diameter less than 100 nm and anaspect ratio of greater than 3:1. The attractiveness of cobalt increasesas the size of the interconnect cavity decreases to 50 nm, 30 nm orbelow having aspect ratios of greater than 3:1, such as between 4:1 and10:1 or higher. For example the method may be implemented to produce asemiconductor integrated circuit device comprising a semiconductor basestructure having a plurality of cavities therein, wherein each cavity ofsuch plurality of cavities has a width or diameter of not greater than20 nm and is filled with cobalt by electrodeposition over a seminalconductive layer of a given thickness on the interior wall of thecavity. Cavities can be filled having entry dimensions (width ordiameter) as small as 7 nm or even 4 nm and aspect ratios of greaterthan 15:1, greater than 20:1 or even greater than 30:1, for example,between 10:1 and 50:1, or between 15:1 and 50:1.

Because the use of cobalt allows a barrier layer to be dispensed with,the volume of cobalt with which a via or trench having a width ordiameter of 20 nm or less may be filled substantially exceeds the volumeof copper with which the same feature may be filled. For example, if therequisite thickness of the barrier layer under a copper deposit is 30angstroms, the volume of cobalt (including, e.g., a 20 angstrom seedlayer) with which a feature having a width or diameter of 20 nm or maybe filled typically exceeds the volume of copper (also including a 20angstrom seed layer) with which the same feature may be filled by atleast 50%, more typically at least 100%. This relative differenceincreases as the size of the feature is further decreased.

The compositions and methods described herein enable cobalt filling ofsubmicron features having an electrical resistance that is competitivewith copper. For example, depending on the thickness of a barrier layernecessary to prevent diffusion and electromigration of copper, a cavityhaving a width or diameter (entry dimension) less than 15 nm may befilled with cobalt over a seminal conductive layer of a given thicknesson an interior wall of the cavity in such volume that the cobalt fillinghas an electrical resistance not more than 20% greater than a referencefilling provided by electrodeposition of copper over a seminalconductive layer of the same given thickness on the interior wall of areference cavity of the same entry dimension as the cobalt filledcavity, wherein a barrier layer against copper diffusion underlies theseminal conductive layer in the reference cavity. For example, thethickness of the barrier layer may be at least 30 angstroms. At entrydimensions significantly lower than 15 nm and/or reference barrier layerthicknesses greater than 30 angstroms, the electrical resistance of thecobalt filling can be significantly less than the electrical resistanceof the reference copper filling. The utility of the cobalt filling asmeasured by its resistance relative to a copper filling becomes mostpronounced in features having a width or diameter not greater than 10nm, or not greater than 7 nm.

The advantage of filling submicron interconnects with cobalt rather thancopper can be illustrated by reference in FIG. 1. The narrow width ofthe via or trench is necessarily further narrowed by the need to providea seminal conductive layer for electrodeposition of the metal that fillsthe interconnect feature. Where the feature is to be filled with copper,the available space within the feature is further diminished by thebarrier layer indicated in FIG. 1, which is necessary to preventdiffusion of copper into the semiconductor substrate. However, where thefeature is to be filled with cobalt, the barrier layer can be dispensedwith, thereby materially increasing the volume available to be filledwith metal. The use of a barrier layer may still be necessary if cobaltis used for filling small features that subsequently come in contactwith copper plating baths, which are typically used to fill largerfeatures. Copper can diffuse into a cobalt layer which can then allowthe copper to diffuse into the dielectric. A barrier layer such as TiNis useful to prevent copper diffusion into the dielectric material ifthe cobalt layer will be subsequently exposed to copper plating baths.

A cobalt seed layer can typically be 0.1 to 40 nm thick. However, forfeatures having a width below about 15 nm, it has been found feasible toprovide a cobalt seed layer having a thickness of only about 1 nm at theside wall, about 4 nm at the bottom, and about 10 nm on the upper fieldsurrounding the interconnect feature, thus preserving a maximum volumefor the cobalt fill.

FIG. 1 shows a cobalt fill and deposit into a submicron feature havingthe space between the cobalt fill and the dielectric occupied by themetal seed layer which provides the seminal conductive layer forelectrodeposition, and the optional barrier layer. There are otherpreferred embodiments where no such barrier layer is used. The barrierlayer is essential when the feature is filled with copper, but notnecessary where the feature is filled with cobalt in accordance withthis invention.

A preferred product of the novel method comprises a semiconductorintegrated circuit device comprising a semiconductor base structurehaving a plurality of cavities therein, wherein each cavity of suchplurality of cavities has an entry dimension of not greater than 15 nmand is filled with cobalt over a seminal conductive layer of a giventhickness on the interior wall of the cavity, e.g., at least 20angstroms. The electrical resistance of the cobalt filling is not morethan 20% greater than a reference filling provided by electrodepositionof copper over a seminal conductive layer of the same given thicknesslocated over a barrier layer on the interior wall of a reference cavityof the same entry dimension, the barrier layer typically having athickness of at least 30 angstroms. Preferably, each cavity of theplurality of cavities has an entry dimension of not greater than 12 nm,not greater than 9 nm, not greater than 8 nm, not greater than 7 nm ornot greater than 4 nm, or between about 5 nm and about 15 nm. The aspectratio of the cavities is at least about 3:1, at least about 4:1, atleast about 15:1, at least about 20:1 or at least about 30:1, typicallybetween about 10:1 and about 50:1.

In preferred embodiments of the semiconductor integrated circuit device,the electrical resistance of the cobalt filling is equal to or less thanthe resistance of the reference copper filling. Internal tensile stressin the cobalt filling is not greater than 500 MPa, typically betweenabout 0 and about 500 MPa, or between 0 and about 400 MPa. The stress ofthe deposit is typically measured after annealing the deposit.

The following non-limiting examples illustrate the invention.

Example 1

-   -   An electrolytic cobalt deposition composition was prepared with        the following components:        -   Co²⁺ ions—2.95 g/L        -   H₃BO₃—30 g/L        -   Ethoxylated propargyl alcohol—20 mg/L        -   Tetronic 1307 (ethoxylated, propoxylated ethylene            diamine)—1000 mg/L        -   water to balance to 1 L        -   pH adjusted to 3.0

Example 2

-   -   An electrolytic cobalt deposition composition was prepared with        the following components:        -   Co²⁺ ions—2.95 g/L        -   H₃BO₃—30 g/L        -   Ethoxylated propargyl alcohol—50 mg/L        -   Tetronic 1307 (ethoxylated, propoxylated ethylene            diamine)—1000 mg/L        -   Vinylphosphonic acid—200 mg/L        -   water to balance to 1 L        -   pH adjusted to 3.0

Example 3

-   -   An electrolytic cobalt deposition composition was prepared with        the following components:        -   Co²⁺ ions—2.95 g/L        -   H₃BO₃—30 g/L        -   Ethoxylated propargyl alcohol—50 mg/L        -   Sodium propargyl sulfonate—200 mg/L        -   water to balance to 1 L        -   pH adjusted to 3.0

These compositions were used to fill a feature having a 12 nm topopening, a 7 nm middle width, a 2 nm bottom width, and a depth of 180 nmat a current density range of 0.1 mA/cm² to 20 mA/cm² with multi-stepcurrent waveform or ramping current waveform, followed by 5 mA/cm² to 20mA/cm² for 0.5-2 minutes, at room temperature and a rotation rate of 20to 200 rpm. The cold entry method was used for 0.5 to 30 seconds

In all examples, void-free fill was achieved with good uniformity.Resistivity is an important factor wherein the current standard requiresthat deposits both with and without additives (VMS only) to have similarresistivity. Resistivity of the deposits plated in the examples abovewas similar to a deposit plated from VMS alone, without any additives.Total impurities of C, O, N, Cl and S were <5000 ppm by weight indeposit. These plating baths are low or sulfur-free compositions and canfill 7 nm openings with an aspect ratio of about 20 for trenches.

A main purpose of the invention described herein is to have seam-freeand void-free fill with good uniformity and film properties. Filmproperties include acceptable stress, good resistivity and minimalimpurities. Uniformity includes having uniform deposit thicknessdistribution over wafer, uniform local fill level and overplate (overisolated and densely placed structures) and smooth morphology.

When introducing elements of the present invention or the preferredembodiment(s) thereof, the articles “a”, “an”, “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements. Substantially free and essentially free, if not otherwisedefined above for a particular element or compound, means that a givenelement or compound is not detectable by ordinary analytical means thatare well known to those skilled in the art of metal plating for bathanalysis. Such methods typically include atomic absorption spectrometry,titration, UV-Vis analysis, secondary ion mass spectrometry, and othercommonly available analytical methods.

As used herein, the term “about” refers to a measurable value such as aparameter, an amount, a temporal duration, and the like and is meant toinclude variations of +1-15% or less, preferably variations of +/−10% orless, more preferably variations of +/−5% or less, even more preferablyvariations of +/−1% or less, and still more preferably variations of+/−0.1% or less of and from the particularly recited value, in so far assuch variations are appropriate to perform in the invention describedherein. Furthermore, it is also to be understood that the value to whichthe modifier “about” refers is itself specifically disclosed herein.

As various changes could be made in the above without departing from thescope of the invention, it is intended that all matter contained in theabove description and shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense. The scope ofinvention is defined by the appended claims and modifications to theembodiments above may be made that do not depart from the scope of theinvention.

1. A composition for the electrolytic deposition of cobalt comprising: asource of cobalt ions; an acetylenic suppressor compound, wherein theacetylenic suppressor compound is an acetylenic alcohol compound or aderivative thereof having a terminal triple bond; a buffering agent; anda uniformity enhancer, wherein the uniformity enhancer comprises anaminic polyol compound or a derivative thereof; and optionally, adepolarizing compound; wherein the composition does not contain anaccelerator; wherein the composition has a concentration of divalentsulfur compounds of less than 1 mg/L.
 2. A composition according toclaim 1, wherein the composition is at least substantially free of anyfunctional concentration of reducing agents that are capable of reducingcobaltous ions (Co²⁺) to metallic cobalt (Co⁰).
 3. A compositionaccording to claim 1 further comprising a stress reducer, wherein thestress reducer comprises saccharin, at a concentration of between about10 and about 300 ppm.
 4. (canceled)
 5. (canceled)
 6. A compositionaccording to claim 1, wherein the acetylenic suppressor compound isselected from the group consisting of propoxylated propargyl alcohol,ethoxylated propargyl alcohol, a reaction product of ethoxylatedpropargyl alcohol and 1,4-butanediol diglycidyl ether, diethylene glycolbis(2-propynyl) ether, and combinations of one or more of the foregoing.7. A composition according to claim 6, wherein the acetylenic suppressorcompound comprises ethoxylated propargyl alcohol.
 8. A compositionaccording to claim 1, wherein the buffering agent comprises boric acid.9. A composition according to claim 1, wherein the pH is between about1.5 and about
 7. 10. A composition according to claim 9, wherein the pHis between about 2.5 and about 3.5.
 11. A composition according to claim1, comprising: between about 1 and about 50 g/L cobalt ions; betweenabout 1 and about 100 mg/L of the acetylenic suppressor compound;between about 10 and about 4000 mg/L of the uniformity enhancer; betweenabout 5 and about 50 g/L buffer; and the balance substantially water.12. A composition according to claim 11, comprising: between about 5 andabout 10 g/L cobalt ions; between about 15 and about 65 mg/L of theacetylenic suppressor compound selected from the group consisting ofpropargyl alcohol and ethoxylated propargyl alcohol; between about 1000and about 4000 mg/L of the uniformity enhancer; between about 15 andabout 40 g/L buffer; and the balance substantially water.
 13. Acomposition according to claim 1 comprising less than about 20 ppbcopper ions.
 14. (canceled)
 15. A composition according to claim 1,wherein the uniformity enhancer is selected from the group consisting ofethoxylated, propoxylated triisopropanolamine, ethoxylated, propoxylatedethylene diamine, ethoxylated, propoxylated diethylene triamine,ethoxylated, propoxylated triethylenetetramine and combinations of oneor more of the foregoing.
 16. A composition according to claim 1,wherein the depolarizing compound is present and is selected from thegroup consisting of sodium propargyl sulfonate, acetylenedicarboxylicacid, acrylic acid, propiolic acid, and mixtures thereof.
 17. Acomposition according to claim 16, wherein the depolarizing compoundcomprises sodium propargyl sulfonate.
 18. A method for electroplating acobalt deposit onto a semiconductor base structure, wherein thesemiconductor base structure comprises a metallizing substratecomprising submicron-sized electrical interconnect features, the methodcomprising the steps of a) contacting the metallizing substrate with anelectrolytic composition comprising: a source of cobalt ions; anacetylenic suppressor compound, wherein the acetylenic suppressorcompound is an acetylenic alcohol compound or a derivative thereofhaving a terminal triple bond; a buffering agent; and a uniformityenhancer, wherein the uniformity enhancer comprises an aminic polyolcompound or a derivative thereof; optionally, a depolarizing compound;wherein the composition does not contain an accelerator; and wherein thecomposition is at least substantially free of divalent sulfur compounds;and b) supplying electrical current to the electrolytic composition todeposit cobalt onto the base structure and fill the submicron-sizedelectrical interconnect features with cobalt.
 19. The method accordingto claim 18, wherein the electrolytic composition is at leastsubstantially free of any functional concentration of reducing agentscapable of reducing cobaltous ions (Co²⁺) to metallic cobalt (Co⁰). 20.The method according to claim 18, wherein the electrolytic compositionis at least substantially free of copper ions, nickel ions, and ironions.
 21. The method according to claim 18, wherein the acetylenicsuppressor compound is selected from the group consisting of propargylalcohols, ethoxylated propargyl alcohol, a reaction product ofethoxylated propargyl alcohol and 1,4-butanediol diglycidyl ether,diethylene glycol bis(2-propynyl) ether,1,4-bis(2-hydroxyethoxy)-2-butyne, 2-butyne-1,4-diol, ethoxylated and/orpropoxylated propargyl alcohol compounds and mixtures of one or more ofthe foregoing.
 22. The method according to claim 21, wherein theacetylenic suppressor compound comprises ethoxylated propargyl alcohol.23. (canceled)
 24. The method according to claim 18, wherein theuniformity enhancer is selected from the group consisting ofethoxylated, propoxylated triisopropanolamine, ethoxylated, propoxylatedethylene diamine, ethoxylated, propoxylated diethylene triamine,ethoxylated, propoxylated triethylenetetramine and combinations of oneor more of the foregoing.
 25. The method according to claim 18, whereinthe electrolytic composition has a pH between about 1.5 and about
 7. 26.The method according to claim 25, wherein the electrolytic compositionhas a pH between about 2.5 and about 3.5.
 27. The method according toclaim 18, wherein the electrolytic composition further comprises astress reducer, wherein the stress reducer comprises saccharin in aconcentration between about 10 and about 300 ppm.
 28. The methodaccording to claim 18, wherein the submicron-sized electricalinterconnect features comprise cavities in said semiconductor basestructure that are superfilled by rapid bottom-up deposition of cobalt.29. The method according to claim 28, wherein electrodeposition ofcobalt fills the submicron-sized electrical interconnect features fromthe bottom up by rapid bottom-up deposition at a rate of growth in thevertical direction which is greater than a rate of growth in thehorizontal direction.
 30. The method according to claim 18, wherein theinternal tensile stresses in cobalt filling the submicron-sizedelectrical interconnect features are between about 0 and about 500 MPa.31. The method according to claim 18, wherein the entry dimension of thesubmicron-sized electrical interconnect features is less than about 50nm.
 32. The method according to claim 31, wherein the submicron-sizedelectrical interconnect features have an aspect ratio of greater thanabout 3:1 or greater than about 4:1 or between about 4:1 and about 10:1.33. The method according to claim 31, wherein the submicron-sizedelectrical interconnect features have an aspect ratio of greater thanabout 15:1, or greater than about 20:1, or greater than about 30:1 orbetween about 10:1 and about 50:1.
 34. The method according to claim 18,wherein a depolarizing compound is present and is selected from thegroup consisting of sodium propargyl sulfonate, acetylenedicarboxylicacid, acrylic acid, propiolic acid, and mixtures thereof.
 35. The methodaccording to claim 34, wherein the depolarizing compound comprisessodium propargyl sulfonate.
 36. A composition for the electrolyticdeposition of cobalt comprising: a source of cobalt ions; an acetylenicsuppressor compound, wherein the acetylenic suppressor compound is anacetylenic alcohol compound or a derivative thereof having a terminaltriple bond; a buffering agent; and 1000 to 4000 mg/L of a uniformityenhancer, wherein the uniformity enhancer comprises an aminic polyolcompound or a derivative thereof; and optionally, a depolarizingcompound; wherein the composition does not contain an accelerator;wherein the composition has a concentration of divalent sulfur compoundsof less than 1 mg/L.